For action, it's basically as you please. Buy some weapons and armor (if you're nice to people and run errands and perform tasks, you'll get cash and other rewards), and you can choose to walk from town to town (instead of, say, riding the Silt Strider, which is quick and safe transportation, but nets no gaining of skills) and kill all manner of creatures along the way.
You can also break into peoples houses to steal, take on entire towns if you please (just remember to get strong first, guards are well-armored), conduct raids, and so on. You can kill literally everyone (actually, I think there might be one person in the game you can't kill, if I remember the list right), so if you don't mind getting a bounty on your head (or plan on it), you can just kill a shopowner and steal stuff (careful, many of the better places have guards who don't take kindly to that).
There are bandits to kill, and areas that you can clear out. Pretty much attack what you want, so long as you're aware of the consequences (bounty and low reputation, which will affect how people treat you and the prices you'll pay at stores).
I couldn't really tell you about magic, as I haven't experimented in that at all (aside from a "turn invisible" power I have), but you can have all sorts of fun with it from what I see.
There's tons of action if you want, though creatures are placed kind of spasely (so don't expect travelling to be a slaughter-fest, but you will kill plenty), but as you get stronger, you'll be able to fight more and take on larger enemies and stronger people. It's slow at first, but patience and planning has it's rewards.
